geochemistry, study of the chemical changes on the earth. More specifically, it is the study of the absolute and relative abundances of chemical elements in the minerals, soils, ores, rocks, water, and atmosphere of the earth and the distribution and movement of these elements from one place to another as a result of their chemical and physical properties. Geochemical studies also include the study of isotopes of chemical elements, especially their abundance and stability in the universe. Geochemistry provides a theoretical basis for ore prospecting and has refined and improved the methods of determining the age of rocks including the use of radioactive isotopes to date the rock. Chemical studies of ancient sedimentary rocks and the fluids contained in them have provided insights into the evolution of the oceans and the atmosphere. Experiments have been conducted with gases that recreate the primordial atmosphere. Today, important work in geochemistry involves the study of geochemical cycles in the atmosphere; marine and estuarine waters; and the earth's crust. There are many studies in relation to the effects of massive amounts of pollutants on the environment.

See K. B. Krauskopf, Introduction to Geochemistry (1967); G. Faure, Principles and Applications of Geochemistry (1991).

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